With the increased price of fuel and electricity, efficient temperature control of buildings is increasingly important. Room temperature control typically utilizes a “temperature span” method, in which a temperature range is specified between a setpoint temperature plus a fixed span temperature and the setpoint temperature minus the fixed span temperature. When heating a room, a heating unit turns off when the room temperature is higher than the setpoint temperature plus span temperature and turns on when room temperature is lower than the setpoint temperature minus span temperature. Similarly, when cooling the room, a cooling unit turns off when the room temperature is lower than the setpoint temperature minus span temperature and turns on when the room temperature is higher than the setpoint temperature plus span temperature. This approach is not very flexible and typically does not adapt to the characteristics of the room or changing environmental factors, thus lowering the efficiency of the cooling or heating unit. This approach is limited by the inherent span temperature resolution, which is dependent on hardware of an electronic digital thermostat, e.g., an analog to digital (A/D) converter, causing an error in the room temperature. Moreover, with thermal time delays of the controlled room and of the thermostat housing, the temperature span setting in the electronic digital thermostat is usually not achievable. Consequently, prior art temperature control often results in a large swing in the room temperature which is not comfortable to the user and may also lead to lower efficiency.
Consequently, there is a need to control a temperature of a room that is sufficiently accurate and that provides improved energy efficiency.